According to Patreaus and the CIA they didn't want to tip off the terrorists they knew who they were so they could monitor them. I posted this yesterday.

Quote:

David H. Petraeus, the former director of the Central Intelligence Agency, told lawmakers on Friday that classified intelligence reports revealed that the deadly assault on the American diplomatic mission in Libya was a terrorist attack, but that the administration refrained from saying it suspected that the perpetrators of the attack were Al Qaeda affiliates and sympathizers to avoid tipping off the groups.

Mr. Petraeus, who resigned last week after admitting to an extramarital affair, said the names of groups suspected in the attack — including Al Qaeda’s franchise in North Africa and a local Libyan group, Ansar al-Shariah — were removed from the public explanation of the attack immediately after the assault to avoiding alerting the militants that American intelligence and law enforcement agencies were tracking them, lawmakers said.

The talking points initially drafted by the C.I.A. attributed the attack to fighters with Al Qaeda in the Islamic Maghreb, the organization’s North Africa franchise, and Ansar al-Shariah, a Libyan group, some of whose members have Al Qaeda ties.

Mr. Petraeus and other top C.I.A. officials signed off on the draft and then circulated it to other intelligence agencies, as well as the State Department and National Security Council.

At some point in the process — Mr. Petraeus told lawmakers he was not sure where — objections were raised to naming the groups, and the less specific word “extremists” was substituted.